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Radiogenic helium in shallow groundwater within a clay till, southwestern Ontario

Amy L. Sheldon·D. Kip Solomon·Robert J. Poreda·Andrew G. Hunt
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Abstract

Profiles of 4 He in pore water were measured in clay aquitards in SW Ontario. The 4 He distributions are consistent with groundwater velocities that are <6 mm yr −1 , and thus diffusion is the dominant transport mechanism for 4 He. Modeling indicates that the effective diffusion coefficient for 4 He is 6.3 ± 1.6 × 10 −6 cm 2 s −1 . Furthermore, the profiles are consistent with the internal release of 4 He from aquitard sediments at a rate of 0.03–0.13 μcc(STP) kg −1 yr −1 . These rates are also consistent with laboratory release experiments and, on average, are 600 times greater than the production of 4 He from U/Th decay. Modeling and the ratio of 21 Ne to 4 He within the sediments indicate that although the aquitards were deposited about 13 kA BP, the sediments released >70% of initial 4 He for 50 to 60 kA prior to incorporation into the till.

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Amy L. Sheldon, D. Kip Solomon, Robert J. Poreda, Andrew G. Hunt. 2003-12-03. Radiogenic helium in shallow groundwater within a clay till, southwestern Ontario. https://doi.org/10.1029/2002wr001797

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